1. Field of Invention
The present invention relates to cooling systems of power circuitry, and more particularly to the thermionic cooling of voltage regulator and/or loads.
2. Description of Related Art
In electronic circuits the flow of current is inseparably accompanied by the production of heat by the resistive circuit elements. In modem electronic circuitry the feature size is ever decreasing. Correspondingly, the current densities and resistances are increasing, leading to a rapid increase of the produced heat. The increased amount of heat needs to be removed from the circuitry for sustainable operations.
Cooling systems can be based on circulating coolant fluids by a compressor through a system of valves and pipelines. Much of today""s refrigeration technology is based on this design. However, using fluids, valves, motors and other moveable parts in electronic circuits requires the integration of rather incompatible technologies. Therefore, other cooling systems are sought.
Electronic cooling systems can be categorized as passive and active systems. Passive systems typically couple the heat source (the electronic circuitry) to a heat sink. Sometimes the heat source is referred to as cold plate, and the heat sink as hot plate. In these systems the heat is conducted from the hotter source to the colder sink driven by the temperature, or thermal, gradient, according to basic laws of thermodynamics. In some systems the heat sink is in direct contact with the environment, exchanging the excess heat by heat conduction and heat convection. In other systems the heat sink is cooled by a fan or by analogous methods. For example in many of today""s computers, microprocessors are cooled with a fan.
However, in these systems the rate of heat transfer is typically slow. Furthermore, passive systems are incapable of transferring heat from a colder place to a hotter one. Therefore, the source always remains hotter than the sink.
Active systems employ an active heat pump or an equivalent of it, which enhances the heat transfer from the source to the sink. Therefore, the flow of heat is faster than in passive systems, in which heat is transferred solely by thermal gradients. Moreover, these active systems can operate to transfer heat from a colder source to a warmer sink.
In some active systems the heat pump drives the xe2x80x9chotxe2x80x9d electrons of the source to a remote area of the circuit, which acts as a heat sink. While heat is transferred away from the heat source by driving away hot electrons, often the atoms and even some of the electrons of the host material conduct the heat back to the source area. This back-flow poses a strong limitation on the efficiency of these systems.
Briefly and generally, embodiments of the invention include a power circuitry with a thermionic cooling system. Some embodiments include a voltage regulator and a heat rectifying device, operable to cool the voltage regulator. Some embodiments of the heat rectifying device include a heat collector and a heat barrier, formed between the voltage regulator and the heat collector, wherein electrons from the voltage regulator are enabled to tunnel across the heat barrier onto the heat collector by an auxiliary voltage.
In some embodiments the heat rectifying device includes a heat collector and a heat barrier, formed between the voltage regulator and the heat collector. The heat barrier prevents the back-flow of heat from the heat collector to the voltage regulator. An auxiliary voltage generator applies an auxiliary voltage between the voltage regulator and the heat collector, enabling the hot electrons of the voltage regulator to tunnel onto the heat collector through the heat barrier. Some embodiments also include a heat sink, coupled to the heat collector and a fan to cool the heat sink. Some embodiments include a controller, controlling the voltage regulator and the heat rectifying device.
In some embodiments the voltage regulator includes a voltage controller and one or more power transistors. The power circuitry can be positioned on a shared substrate, which is shared by the voltage controller and the power transistors. In some embodiments the voltage controller keeps a temperature of at least one of the power transistors, the heat collector, the heat sink, and the shared substrate in a preselected range by controlling at least one of the power transistors, the auxiliary voltage generator, and a fan, positioned to cool the heat sink.
In some embodiments a load is integrated together with the cooling system so that the load itself can be cooled by the heat rectifying device. In some embodiments the voltage regulator is capable of operating at a power density of more than 5,000 W/cm2.